Mechanical linkage arrangements incorporating bell cranks can be used to provide rotational control of annular arrays of vanes in multiple stages in a compressor of a gas turbine engine. Such an arrangement may comprise a bell crank, rotatable about a fulcrum, an actuation rod being pivotably connected to an input arm to the bell crank and a control rod being pivotably connected to an output arm of the bell crank. Movement of the actuation rod rotates the bell crank which in turn causes motion of the control rod. This motion can then be used to drive a unison ring which changes the angles of a row of vanes. Existing linkage arrangements can provide linked behaviour between the different rows of vanes.